The present invention relates to swivel joints. More particularly, the present invention relates to a swivel joint for transferring tension and compression forces.
Universal joints are well-known devices that couple members together, yet allow motion in two degrees of freedom. Commonly, the universal joint includes two yokes or devises with a cross or spider member disposed therebetween. Bearing surfaces on ends of the spider allow relative angular motion about two orthogonal axes.
Universal joints can be used in a variety of different applications. In many instances, the universal joint is used to transfer torque loads between coupled members. However, an universal joint having high axial stiffness for transmitting tension and compression forces would be particularly beneficial for yet other applications. However, current universal joints experience low strength and stiffness in the axial direction due to bending stresses and deflection of the spider.
A swivel joint according to one aspect of the present invention includes first and second base members. A spider further includes first and second arcuate surfaces that form joints with the first and second base members, respectively. Furthermore, the spider includes first and second pins opposed from each other and third and fourth pins opposed from each other. A first mechanism, coupling the spider and the first base member, is adapted to effect a compressive force between the first base member and the first arcuate surface. Also, a second mechanism, coupling the spider and the second base member, is adapted to effect a compressive force between the second base member and the second arcuate surface. The forces between the base members and the corresponding arcuate surfaces maintain coupling of the base members and the corresponding arcuate surfaces when subjected to external working forces, thereby preserving axial stiffness throughout the working force range in tension and compression and through the range of motion of the joint.